In 1872 the HMS Challenger pulled out from Portsmouth, England to begin an unprecedented scientific expedition of the world’s oceans. During its over three year journey the HMS Challenger not only collected thousands of new species and sounded unknown ocean depths, but also took hundreds of temperature readings—data which is now proving invaluable to our understanding of climate change.

Utilizing the temperature data from the HMS Challenger expedition and comparing it to contemporary temperatures, researchers writing in Nature Climate Change found that the oceans’ surface— where marine warming is most intense—saw temperature rise on average by 0.59 degrees Celsius (1.1 degrees Fahrenheit) over the past 135 years or so. This implies that oceanic temperatures have been rising for at least a century.